Modern aircraft rely on multiple radio systems to provide information to the pilot. For example, an aircraft may include radio systems such as distance measuring equipment (DME), transponder system equipment including the air traffic control radar beacon system (ATCRBS) and Mode-S systems, and automatic dependence surveillance-broadcast (ADS-B) system equipment such as universal access transceivers (UAT), 1090 MHz extended squitters and UHF digital link (VDL) Mode 4.
Distance measuring equipment (DME) is used to determine the distance between an aircraft and a ground station. The transmitter for DME operates in the 978-1212 MHz range. The transmitter sends out narrow pulses that are received by the ground station, which returns a reply pulse transmission. The reply pulses are received by the DME receiver which calculates distance to the ground station by the elapsed time between the sending of the initial pulse to reception of the reply pulse.
In transponder systems, an interrogation signal is received at a transceiver on the aircraft and a reply to the interrogation signal is sent to the entity that sent the interrogation signal, such as a ground station. One transponder system is the ATCRBS. The ATCRBS is designed to send, in reply to an interrogation signal, information from an aircraft regarding identification of the aircraft and the altitude of the aircraft. In operation, an aircraft transponder, which includes a transceiver, receives an interrogation signal sent at a frequency of 1030 MHz. The interrogation signal is typically received at regular intervals from a ground station. After receiving the interrogation signal, the transponder determines a response and transmits a reply. In one embodiment, the reply comprises an identification of the aircraft transmitted as a series of timed pulses. The ground station decodes the reply to obtain the identification of the aircraft. Also, the ground station can calculate the range to the aircraft based on the round trip time between the sending of the interrogation pulse and the reception of the reply. The altitude of the aircraft can be determined based on the direction the antenna of the ground station was facing when the reply was received.
Another type of transponders are Mode-S transponders. Mode-S transponders operate on the same frequency as ATCRBS transponders but represent a significant improvement over older transponder systems in that interrogations can be sent to specific aircraft.
ADS-B system equipment on an aircraft sends out messages without first receiving an interrogation. These messages can be received by other aircraft and by ground station devices. ADS-B systems can periodically broadcast the aircraft's altitude, velocity and other information. In the United States two different ways of implementing ADS-B have been approved by the Federal Aviation Authority: 1090 MHz Mode-S extended squitters (ES) and universal access transceivers (UAT). 1090 MHZ ES have been chosen for use in commercial aircraft and UAT have been chosen for use in general aviation applications.
In a 1090 MHz ES system a 1090 transmitter can be used to periodically transmit ES messages. ES messages from other 1090 MHz systems can be received by the 1090 MHz system. The ES message can comprise such information as position, velocity and heading. UAT systems broadcast messages at 978 MHz (in the U.S.) and receive messages from other UAT systems at the same frequency. UAT messages can comprise information such as that sent in 1090 MHz ES messages, as well as other information, such as traffic information from other aircraft and flight information from ground stations.
Each of the various radio systems, DME systems, transponder systems and ADS-B systems provide valuable information to the operator of the aircraft. Unfortunately, each system is deployed separately as each radio system requires its own receiver, its own transmitter, and its own antenna and each radio system operates at a specific frequency. This adds weight to the aircraft and requires additional space to house the multiple radios.
Accordingly, it is desirable to provide a method and apparatus for a multifunction radio. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.